Skin Resurfacing at 1930 NM

ABSTRACT

Non-ablative skin resurfacing can include generating electromagnetic radiation having a wavelength of about 1920 nm to about 1950 nm and a fluence of about 3 J/cm 2  to about 6 J/cm 2 . The electromagnetic radiation is delivered to a target region of skin to cause thermal injury to the epidermis in the target region sufficient to elicit a healing response that produces a substantially improved skin condition without detachment of the epidermis (e.g., within 3 days of treatment).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication Ser. No. 61/166,582 filed Apr. 3, 2009, which is owned bythe assignee of the instant application and the disclosure of which isincorporated herein by reference in its entirety. This application is acontinuation of U.S. Ser. No. 12/754,374 filed Apr. 5, 2010, the entirecontent of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to skin resurfacing (e.g., improvingskin texture and wrinkles) at about 1930 nm, and more particularly tocausing thermal injury in the epidermal and/or dermal region of the skinsufficient to elicit a healing response that produces a substantiallyimproved skin condition, while leaving the epidermis substantiallyintact, at about 1930 nm.

BACKGROUND OF THE INVENTION

CO₂ and Er:YAG laser systems can be used for ablative skin resurfacing.The ablative CO₂ and Er:YAG technologies promote epidermal regenerationand collagen remodeling by removal of the epidermis accompanied bydermal contraction and remodeling. The CO₂ laser produces thermal damageextending from 70 to 180 um into the dermis. However, because of highmorbidity, significant down time and prolonged recovery period, theyhave decreased in popularity.

Non-ablative procedures were developed to minimize adverse effect anddown time. These technologies protect the epidermis from laser inducedthermal injury and leave the outer skin layer intact, typically throughaggressive skin cooling. Thermal injury occurs at the deeper dermalstructures to induce a wound healing process and remodeling. Forexample, the 1540 nm wavelength Er:Glass laser produces a mean depth ofinjury of about 700 μm. However, some patients want more noticeableresults with fewer treatments.

SUMMARY OF THE INVENTION

The invention, in one embodiment, features skin resurfacing (e.g.,improving skin texture and wrinkles) at about 1930 nm. A treatment cancause thermal injury in the epidermal and/or dermal region of the skinsufficient to elicit a healing response that produces a substantiallyimproved skin condition, while leaving the epidermis substantiallyintact. In certain embodiments, only the epidermis is damaged (fullthickness damage or only a portion of the epidermis). In certainembodiments, the full thickness of the epidermis and an upper portion ofthe dermis are damaged. In certain embodiments, a portion of theepidermis and an upper portion of the dermis are damaged. The skinresurfacing is non-ablative.

The 1930 nm wavelength is substantially absorbed by water in theepidermis or dermis. A treatment can match or substantially match thepenetration depth of the light to the thickness of the epidermis. The1930 nm wavelength is absorbed by skin more strongly than non-ablativewavelengths and less strongly than ablative wavelengths. The 1930 nmwavelength penetrates shallower than typical non-ablative wavelengthsand deeper than ablative wavelengths. As a result, a treatment using1930 nm can substantially volumetrically heat the whole layer thicknessof the epidermis, which can not be achieved at longer or shorterwavelengths. Ablative wavelengths that heat to the same depth as the1930 nm wavelength result in unwanted ablation of the skin. Non-ablativewavelengths are focused below the epidermis.

The treatment need not immediately ablate the skin. The treatment canleave the skin intact for up to 3 days before the skin begins todesquamate. The treatment can leave the skin intact for at least 3 daysbefore the skin begins to desquamate. In certain embodiments, thetreatment leaves the skin intact for up to 7 days before the skin beginsto desquamate. Higher fluence treatments result in more immediatedesquamation. The treatment can leave the skin intact for at least 6hours, 12 hours, 18 hours, 1 day, 2 days, 3 days, 4 days, 5 days, 6days, 7 days, or longer before the skin begins to desquamate. Thetreatment can cause a thermal damage zone while keeping the epidermisdamaged but intact. The damaged intact epidermis can create a naturalprotective dressing on the skin that remains during the restorativeprocess. This speeds healing time and results in less downtime. Anadditional advantage of such a treatment is that the treatment can beperformed with minimal acute cosmetic disturbance so that the patientcan return to normal activity immediately after the treatment.

A treatment can include cooling to protect the skin surface to minimizeunwanted injury to the surface of the skin and to minimize any pain thata patient may feel. Cooling, however, is not required. If cooling isused, only superficial cooling is affected so that a portion of theepidermis can be treated. For example, the most superficial layer(s) orportion of the epidermis is cooled, so that it remains intact, while alower portion of the epidermis is damaged.

Control and specificity of full thickness or substantially fullthickness damage of the epidermis has not been previously demonstratedusing ablative or non-ablative wavelengths. Furthermore, control andspecificity of full thickness or substantially full thickness damage ofthe epidermis has not been previously disclosed or demonstrated usingthe 1930 nm wavelength. Non-ablative skin resurfacing at or about 1930nm has not been demonstrated.

While the use of water as a chromophore, infrared wavelengths and wideranges of fluences have been suggested for skin resurfacing, previouspractitioners have not recognized the unexpected benefits, theeffectiveness, or the criticality of matching the damage to thethickness of the epidermis and utilizing 1930 nm for skin resurfacing.Indeed, practitioners have taught against the use of 1930 nm, e.g.,suggesting that radiation should be focused in the upper dermis orteaching to ablate the epidermis.

In one aspect, there is a method of non-ablative skin resurfacing.Electromagnetic radiation is generated having a wavelength of about 1920nm to about 1950 nm and a fluence of about 3 J/cm² to about 6 J/cm², anddelivered to a target region of skin. Thermal injury is caused to theepidermis in the target region sufficient to elicit a healing responsethat produces a substantially improved skin condition without detachmentof the epidermis.

In another aspect, there is a method of non-ablative skin resurfacing.Electromagnetic radiation is generated having a wavelength of about 1920nm to about 1950 nm and a fluence of about 3 J/cm² to about 6 J/cm², anddelivered to a target region of skin. Thermal injury is caused to theepidermis and to the dermis in the target region sufficient to elicit ahealing response that produces a substantially improved skin conditionwithout detachment of the epidermis.

In yet another aspect, there is a method of non-ablative skinresurfacing. Electromagnetic radiation is generated having a wavelengthof about 1930 nm and a fluence of up to 5 J/cm², and delivered to atarget region of skin. Thermal injury is caused to the epidermis in thetarget region sufficient to elicit a healing response that produces asubstantially improved skin condition without detachment of theepidermis.

In still another aspect, there is a method of non-ablative skinresurfacing. Electromagnetic radiation is generated having a wavelengthof about 1920 nm to about 1950 nm, a fluence of about 3 J/cm² to about 6J/cm², and a pulse duration up to 1 second, and delivered to a targetregion of skin. Thermal injury is caused to the epidermis in the targetregion sufficient to elicit a healing response that produces asubstantially improved skin condition without detachment of theepidermis.

In yet another aspect, there is an apparatus for non-ablative skinresurfacing. The apparatus includes means for generating electromagneticradiation, e.g., having a wavelength of about 1920 nm to about 1950 nmand a fluence of about 3 J/cm² to about 6 J/cm². The apparatus includesmeans for delivering the electromagnetic radiation to a target region ofskin. The apparatus includes means for causing thermal injury to theepidermis in the target region sufficient to elicit a healing responsethat produces a substantially improved skin condition without detachmentof the epidermis. The apparatus can include means for causing cellnecrosis to a depth of up to 300 micrometers in the dermis.

In yet another aspect, there is an apparatus including a sourcegenerating electromagnetic radiation having a wavelength of about 1920nm to about 1950 nm and a fluence of about 3 J/cm² to about 6 J/cm², andmeans for receiving the electromagnetic radiation, for absorbing aportion of the electromagnetic radiation to form a plurality ofuntreated zones, and for transmitting the remaining portion of theelectromagnetic radiation to form a region of thermal injury surroundingthe plurality of untreated zones. The means for absorbing theelectromagnetic radiation can be a mask.

In other embodiments, any of the aspects above, or any apparatus, deviceor system or method, process or technique described herein, can includeone or more of the following features.

Thermal injury can be caused while leaving the epidermis intact for upto 3 days or for up to 7 days. Cell necrosis can be caused to a depth ofup to 300 micrometers in the dermis. The epidermis can be left intactfor at least 3 days. The treatment can reduce the appearance ofwrinkles. Thermal injury can be caused to an upper portion of the dermisin the target region of skin. Thermal injury can be caused without acutecosmetic disturbance to the epidermis. Optical penetration depth of theelectromagnetic radiation can be matched to a thickness of theepidermis.

The target region of skin can be exposed to the electromagneticradiation for up to 1 second. The pulse duration can be less than orequal to 250 milliseconds. The pulse duration can be less than or equalto 50 milliseconds. The wavelength of the electromagnetic radiation canbe about 1930 nm or about 1947 nm. A pulsed source or a scanned or gatedcontinuous wave source can be used to generate the electromagneticradiation. A thulium-doped laser (e.g., thulium:YAP) or a diode lasercan be used to generate the electromagnetic radiation. Alternatively, asemiconductor laser or a diode laser can be used to generate theelectromagnetic radiation.

In certain embodiments, a pattern of thermal injuries can be formed inthe target region of skin. A plurality of thermal injuries can beformed. Each thermal injury can be separated from adjacent thermalinjuries by substantially undamaged epidermal tissue. In certainembodiments, a reverse fractional pattern can be formed includingregions of undamaged tissue separated from adjacent regions of undamagedtissue by treated epidermal tissue.

Other aspects and advantages of the invention will become apparent fromthe following drawings and description, all of which illustrateprinciples of the invention, by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the invention described above, together with furtheradvantages, may be better understood by referring to the followingdescription taken in conjunction with the accompanying drawings. Thedrawings are not necessarily to scale, emphasis instead generally beingplaced upon illustrating the principles of the invention.

FIG. 1 shows tissue effects from an exemplary tissue experiment.

FIG. 2 shows tissue effects from another exemplary tissue experiment.

FIG. 3 shows tissue effects from another exemplary tissue experiment.

FIG. 4 shows tissue effects from another exemplary tissue experiment.

FIG. 5 shows tissue effects from another exemplary tissue experiment.

FIG. 6 shows tissue effects from another exemplary tissue experiment.

FIG. 7 shows normal skin.

FIG. 8 is a schematic drawing of an exemplary system for treatingtissue.

FIG. 9 shows an exemplary system that can be used to form a pattern oftreatment zones in skin.

FIG. 10 shows an exemplary embodiment of a delivery module.

FIG. 11 shows a microlens array spaced from the skin.

FIG. 12 shows a sectional view of a skin resurfacing treatment.

FIG. 13 shows a sectional view of another skin resurfacing treatment.

FIG. 14 shows a sectional view of another skin resurfacing treatment.

FIG. 15 shows a top view of the thermal injury caused by the skinresurfacing treatment shown in FIG. 14.

FIG. 16 shows an exemplary mask for forming a reverse fractionalpattern.

FIG. 17 shows a sectional view of a mask 230 for forming a reversefractional pattern.

FIG. 18 shows an exemplary pattern of damage including untreated zonessurrounded by a treatment region.

DETAILED DESCRIPTION OF THE INVENTION

Table 1 shows optical penetration depths for wavelengths commonly usedfor skin resurfacing (ablative and non-ablative) and for the 1930 nmwavelength.

A treatment can damage the epidermis, which can be about 100 μm±50 μm.The 1930 nm wavelength is advantageous because its optical penetrationdepth substantially matches the thickness of the epidermis. Thetreatment can extend into the dermis up to 180 μm, although deepertreatments can be achieved. In certain embodiments, the treatmentextends into the dermis by up to 150 μm, up to 100 μm, up to 50 μm, upto 25 μm, up to 10 μm, up to 5 μm, or up to 2 p.m.

TABLE 1 Optical penetration depths. λ (nm) μ_(a) (cm⁻¹) OPD (μm) 10640845 12 2940 12202 0.8 2790 5882 1.7 1930 130 77 1550 11 909 1450 31 323

Tissue experiments were performed on a porcine model. A 16 W 1930±40 nmdiode laser system (available from Applied Optronics) delivered energyvia a 1.5 mm optical fiber. The pulse duration was up to 1 second. Thelight was reimaged through an optical lens system to about 3.5-4 mm spoton the skin. FIG. 1 shows the tissue effects resulting from radiantexposure of 5.5 J/cm², 4 mm spot size and 250 msec pulse duration. Theresidual thermal damage produced was 100 μm. FIG. 1 also shows that withthe 1930 nm laser radiation, the epidermis is thermally denatured but isnot removed. An intact epidermis acts as a natural protective dressing,speeds healing, reduces down time, and improves clinical results. Injuryof this type can not be achieved using non-ablative or ablativewavelengths. Non-ablative wavelengths result in thermal damage in deeperzones, and ablative wavelengths result in ablation of the epidermis.

FIGS. 2 and 3 show that higher fluences or radiant exposures produceddeeper zones of residual thermal damage. FIG. 2 shows porcine tissuetreated with 8.4 J/cm², 4 mm spot, 250 msec duration. The residualthermal damage produced is 350 μm. FIG. 3 shows porcine tissue treatedwith 11 J/cm², 4 mm spot, 250 msec duration. The residual thermal damageproduced is 550 μm. The residual thermal damage zones shown in FIGS. 2and 3 can create undesired scars or other undesired effects. In FIGS. 2and 3, the epidermis is shown separating from the dermis.

Tissue experiments were performed on a human subjects. Subjects (skintype I-III) were treated with a 1930 nm diode laser. The pulse durationranged between 50-150 ms, laser radiant exposure ranged between 3-5.5J/cm² at a spot size of 3.5 mm. Skin cooling was not used. Each patientreceived 1 treatment.

With higher fluences (>5 J/cm²), immediate thermal damage extending asdeep as 300 microns without ablation of the epidermis was observed.Pyknosis of nuclei in the epidermis was the earliest sign of damage. Twoweek and 2 month biopsies showed only mild fibrosis. Mild erythema atlower fluences and slight vesiculation at the higher fluences wasobserved. No scarring was noted even at sites with early vesiculation.

FIG. 4 shows the tissue effects resulting from 3.6 J/cm², 80 msec at1930 nm. FIG. 5 shows the tissue effects resulting from 4.2 J/cm², 80msec at 1930 nm. FIG. 6 shows the tissue effects resulting from 4.9J/cm², 80 msec at 1930 nm. FIG. 7 shows normal skin.

FIGS. 1 and 4-7 show that a relatively narrow window of wavelength,fluence and pulse duration is available for damaging the epidermiswithout epidermal detachment. The fluence is typically about 3.6 toabout 4.9 J/cm². Full thickness damage of the epidermis can be achievedat 80 milliseconds. Damage to the epidermis and dermis can be achievedat 250 milliseconds. The wavelength can be 1930±40 nm. The spot size canbe about 3-5 mm. By varying the input radiant exposure, one can controlthe effective zone of residual thermal damage and/or confine damage tothe epidermis, while leaving it intact.

In various embodiments, a treatment can, for example, improve skinlaxity, improve skin texture, tighten skin, strengthen skin, thickenskin, induce new collagen formation, promote fibrosis of skin, partiallydenature collagen, treat wrinkles, reduce or minimize the appearance ofwrinkles, treat pigmented lesions, treat vascular lesions, treat acne,treat acne scars, treat striae, or be used for a combination of theaforementioned. Partially denaturing collagen can induce and/oraccelerate collagen synthesis by fibroblasts. For example, causingselective thermal injury can activate fibroblasts, which can depositincreased amounts of extracellular matrix constituents (e.g., collagenand glycosaminoglycans) that can, at least partially, rejuvenate theskin.

The thermal injury caused by the radiation can be mild and onlysufficient to elicit a healing response and cause the fibroblasts toproduce new collagen. Excessive denaturation of collagen in the dermiscauses prolonged edema, erythema, and potentially scarring. Inducingcollagen formation in the target region can change and/or improve theappearance of the skin of the target region, as well as thicken theskin, tighten the skin, improve skin laxity, reduce the severity ofwrinkles and/or reduce discoloration of the skin. Thermal injury neednot include destroying or killing tissue, cells or biomolecules.Instead, thermal injury can be confined to injury or harm whilepreserving the function or activity of the tissue, cells or biomoleculesbeing treated or targeted.

In certain embodiments, thermal injury caused by the radiation can causecell necrosis. For example, the thermal injury can cause cell necrosisin the dermis while leaving the epidermis intact for at least 3 days.The cell necrosis can occur to a depth of up to 700, 500, 300 or 200micrometers in the dermis (although deeper or shallower injury canresult).

FIG. 8 shows an exemplary embodiment of a system 30 for treating tissue.The system 30 can be used to non-invasively deliver a beam of radiationto a target region. For example, the beam of radiation can be deliveredthrough an external surface of skin over the target region. The system30 includes an energy source 32 and a delivery system 33. In oneembodiment, a beam of radiation provided by the energy source 32 isdirected via the delivery system 33 to a target region. In theillustrated embodiment, the delivery system 33 includes a fiber 34having a circular cross-section and a handpiece 36. A beam of radiationcan be delivered by the fiber 34 to the handpiece 36, which can includean optical system (e.g., an optic or system of optics) to direct thebeam of radiation to the target region. A user can hold or manipulatethe handpiece 36 to irradiate the target region. The delivery system 33can be positioned in contact with a skin surface, can be positionedadjacent a skin surface, can be positioned proximate a skin surface, canbe positioned spaced from a skin surface, or a combination of theaforementioned. In the embodiment shown, the delivery system 33 includesa spacer 38 to space the delivery system 33 from the skin surface. Aspacer 38 is not required however. In one embodiment, the spacer 38 canbe a distance gauge, which can aid a practitioner with placement of thedelivery system 33.

Referring to FIG. 8, to minimize unwanted thermal injury to tissue nottargeted (e.g., an exposed surface of the target region and/or theepidermal layer), the delivery system 33 shown in FIG. 8 can include acooling system for cooling before, during or after delivery ofradiation, or a combination of the aforementioned. Cooling can includecontact conduction cooling, evaporative spray cooling (using a solid,liquid, or gas), convective air flow cooling, or a combination of theaforementioned. If cooling is used, it can cool the most superficiallayers of epidermal tissue. Cooling can facilitate leaving the epidermisintact.

FIG. 9 shows an exemplary embodiment of a system 101 that can be used toform a pattern of treatment zones in skin. System 101 can include a baseunit 105 coupled to an umbilicus 110, which is connected to a deliverymodule 115. The base unit 105 includes a power source 120 that suppliespower to an energy source 125. The base unit 105 also includes acontroller 130, which can be coupled to a user interface and can includea processing unit.

The system 101 can be used to non-invasively deliver an array ofradiation beams to a target region of the skin. For example, the arrayof radiation beams can be delivered through an external surface of skinover the target region. In one embodiment, a beam of radiation providedby the energy source 125 is directed via the delivery module 115 to atarget region.

The umbilicus 110 can act as a conduit for communicating power, signal,fluid and/or gas between the base unit 105 and the delivery module 115.The umbilicus 110 can include a fiber to deliver radiation from the baseunit 105 to the delivery module 115. The delivery module 115 can includean optical system (e.g., an optic or a system of optics) to convert thebeam into an array of radiation beams and direct the array to the targetregion. The optical system can include a mask or focusing system toprovide a beam of radiation having regions where no treatment radiationis delivered (e.g., to create a pattern of undamaged tissue or skinsurrounded by damaged tissue or skin). A user can hold or manipulate thedelivery module 115 to irradiate the target region. The delivery module115 can be positioned in contact with a skin surface, can be positionedadjacent a skin surface, can be positioned proximate a skin surface, canbe positioned spaced from a skin surface, or a combination of theaforementioned.

In certain embodiments, an array of radiation beams can be formed from asingle beam of radiation by a system of optics. In various embodiments,the array of radiation beams can be formed from multiple sources. Eachsource can generate one beam of radiation. Multiple sources can becombined to form an array of radiation beams. In certain embodiments,multiple sources can be combined with a system of optics to form anarray of radiation beams.

In certain embodiments, the base unit 105 can have a second source 132of radiation. For example, the source 125 can provide radiation that isabsorbed preferentially in the dermal skin region, and the second source132 can provide radiation that is absorbed preferentially in theepidermal skin region.

FIG. 10 shows an exemplary embodiment of a delivery module 115 connectedto umbilicus 110 via a connector 135. In certain embodiments, connector135 can be a coaxial RF connector such as SMA connector. The deliverymodule 115 includes a skin contacting portion 140 that can be broughtinto contact with the skin 137. The delivery module 115 includes beamsteering optics 142 and 143 and optical element 148. Optics 142 and 143can be mirrors. Optics 142 and 143 can be moved or rotated to direct thebeam of radiation 150 to optical element 148. Optical element 148 can bea microlens array. The optical element 148 can be fixed, removable, orspaced from the skin contacting portion 140. In certain embodiments, theoptical element 148 and skin contacting portion 140 are a singleintegrated unit.

Controller 130 can include a computer program and/or a mechanicaldevice. Controller 130 can be manipulated by a user via a userinterface. The user interface can include a touch screen, liquid crystaldisplay, keypad, electrical connectors, wireless connection or acombination of the afore mentioned features. Other features and devicesthat are known in the art for controlling computer programs andmechanical devices can also be employed.

Controller 130 can move optical element 148 in one or more translationaldirections. After each translational movement, optical element 148delivers the array of radiation beams to the skin to form a sub-patternof injury. Each sub-pattern contributes to the overall pattern oftreatment zones being formed. In certain embodiments, optical element148 is moved in at least three translational directions before thedelivery module 115 is moved to an untreated portion of the skin.

Controller 130 can move at least one of the optics 142 and 143 to movethe array of radiation beams. Controller 130 can move the array in atleast three translational directions before delivery module 115 is movedto an untreated portion of skin.

In this manner, a practitioner need not roll or drag delivery module 115across or along the surface of the skin to effect a treatment. Instead,a practitioner can stamp the delivery module 115 onto the skin surfaceand allow the delivery module 115 to form a pattern of treatment zonesbefore moving the delivery module 115. This allows for more uniformtreatment because a practitioner's experience or hand speed need notaffect the treatment.

To minimize unwanted thermal injury to tissue not targeted (e.g., anexposed surface of the target region and/or the epidermal layer), thedelivery module 115 can include a cooling module for cooling before,during or after delivery of radiation, or a combination of theaforementioned. Cooling can include contact conduction cooling,evaporative spray cooling, convective air flow cooling, or a combinationof the aforementioned.

The skin contacting portion 140 can include a sapphire or glass windowand a fluid passage containing a cooling fluid. The cooling fluid can bea fluorocarbon type cooling fluid, which can be transparent to theradiation used. The cooling fluid can circulate through the fluidpassage and past the window to cool the skin.

As shown in FIG. 11, the delivery module 115 can include one or morespacers 152 to position the delivery module 115 relative to the skin137. For example, the skin contacting portion 140 can be spaced from thesurface of the skin 137 by a distance d. The distance d can be adjustedto control the depth of penetration of the array of radiation beams andthe size of the treatment zones. In one embodiment, the spacer 152 canbe a distance gauge.

In various embodiments, the energy source 32 can be an incoherent lightsource or a coherent light source (e.g., a laser). The energy source canbe broadband or monochromatic. The beam of radiation can be a pulsedbeam, a scanned beam, or a gated continuous wave (CW) beam. The lasercan be a diode laser, a solid state laser, a fiber laser, a cobaltmagnesium laser, or a thulium-doped laser (e.g., a crystal laser such asthulium:YAG or thulium:YAP). An incoherent source can be a lightemitting diode (LED), a flashlamp (e.g., an argon or xenon lamp), anincandescent lamp (e.g., a halogen lamp), a fluorescent light source, oran intense pulsed light system. The incoherent source can includeappropriate filters to block unwanted electromagnetic radiation.

In various embodiments, the beam of radiation has a wavelength of about1890-1970 nm. The wavelength can be about 1920-1950 nm. In certainembodiments, the wavelength is about 1930 nm. In certain embodiments,the wavelength is 1930 nm. In certain embodiments, the wavelength isabout 1947 nm. In certain embodiments, the wavelength is 1947 nm. Afirst source operating at about 1930 nm can be combined with a secondsource operating from about 400 nm to about 10.6 microns, can becombined with an RF source or can be combined an ultrasonic source.

In various embodiments, the beam of radiation can have a fluence ofabout 1 J/cm² and about 10 J/cm², for example, about 2-8 J/cm² or 3-6J/cm². The fluence can be below about 8 J/cm², below about 6 J/cm²,below about 5 J/cm², between about 3.6 to 4.9 J/cm² or between about 3.6to 4.2 J/cm². Above the fluence, excessive damage to the skin occurs.Below the fluence, a treatment does not result in skin resurfacing. Insome embodiments, the fluence is 2-6 J/cm². In certain embodiments, thefluence is 3-5 J/cm².

In various embodiments, the beam of radiation can have a spotsizebetween about 0.1 mm and about 30 mm, although larger and smallerspotsizes can be used depending on the application. The spotsize can beup to 30 mm, up to 25 mm, up to 20 mm, up to 15 mm, up to 10 mm, up to 5mm, or about 3.5-4 mm. In certain embodiments, the spotsize is about 4mm or about 20 mm.

In various embodiments, the beam of radiation can be delivered at a rateof between about 0.1 pulse per second and about 10 pulses per second,although faster and slower pulse rates can be used depending on theapplication.

Radiation can be applied to the skin in a stamping mode or by scanning alight source along a surface of the skin. A computerized patterngenerator can be used or a handpiece can be manually manipulated to scanthe light source.

In various embodiments, the parameters of the radiation can be selectedto deliver the beam of radiation to a predetermined depth. In someembodiments, the beam of radiation can be delivered to the target regionabout 0.005 mm to about 1 mm below an exposed surface of the skin,although shallower or deeper depths can be selected depending on theapplication. In some embodiments, the depth is less than 0.7 mm. In someembodiments, the depth is less than 0.5 mm. In some embodiments, thedepth is less than 0.3 mm. In some embodiments, the depth is less than0.2 mm.

In various embodiments, the tissue can be heated to a temperature ofbetween about 40° C. and about 80° C., although higher and lowertemperatures can be used depending on the application. In oneembodiment, the temperature is between about 55° C. and about 70° C. Inone embodiment, the temperature is between about 50° C. and about 65° C.

In various embodiments, the beam of radiation can have a pulse durationbetween about 10 μs and about 30 s, although larger and smaller pulsedurations can be used depending on the application. In certainembodiments, the beam of radiation can have a pulse duration of about 30milliseconds to about 1 second. The pulse duration can be about 80-250milliseconds. In certain embodiments, a longer pulse duration permits abeam of radiation to penetrate deeper into the epidermis or dermis incomparison to a beam of radiation having a shorter pulse duration,providing that all other parameters are the same.

An optical system can be used to deliver radiation to a large area beamor as a pattern of beamlets (e.g., a plurality of microbeams having aspotsize of about 0.1-2 mm) to form a pattern of thermal injury withinthe biological tissue.

One or more sensors can be positioned relative to a target region ofskin. For example, a sensor can be positioned in contact with, spacedfrom, proximate to, or adjacent to the skin target. A sensor candetermine a temperature on a surface of the target region, in the targetregion, or remote from the target region.

The sensor can be a thermistor, an array of thermistors, a thermopile, athermocouple, a thermometer, a resistance thermometer, and athermal-imaging based sensor, a thermographic camera, an infrared cameraor any combination of the aforementioned.

A treatment apparatus can include a processor, which can be used tocontrol the pattern generation (for delivery of radiation) and/or tocorrelate temperature measured by a sensor to determine the temperaturein or of the target region.

The processor can generate one or more output signals to control theradiation source. For example, if the temperature in the target regionreaches a threshold temperature, the processor can shut off the sourceto cease delivery of the radiation. The threshold temperature can be ata preset, fixed value or programmable according to user instruction. Theprocessor can be coupled to the delivery system, can be integrated withthe delivery system, or can be separate from the delivery system.

Processors suitable for the execution of computer programs include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. A processorcan receive instructions and data from a read-only memory or a randomaccess memory or both. A processor also includes, or be operativelycoupled to receive data from or transfer data to, or both, one or moremass storage devices for storing data, e.g., magnetic, magneto-opticaldisks, or optical disks. Data transmission and instructions can alsooccur over a communications network. Information carriers suitable forembodying computer program instructions and data include all forms ofnon-volatile memory, including by way of example semiconductor memorydevices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks,e.g., internal hard disks or removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks. The processor and the memory can besupplemented by, or incorporated in special purpose logic circuitry.

FIG. 12 shows a sectional view of an exemplary skin resurfacingtreatment. The skin resurfacing can be non-ablative. Electromagneticradiation 170 is directed to skin 175, which includes epidermis 180,dermis 185, and a subcutaneous fat region 190. The electromagneticradiation 170 can cause thermal injury 195 to the epidermis 180 in thetarget region sufficient to elicit a healing response that produces asubstantially improved skin condition without detachment of theepidermis 180. The thermal injury 195 can extend into the dermis 185.The thermal injury 195 can leave the epidermis 180 intact for, e.g., upto 3 days. The optical penetration depth of the electromagneticradiation 170 can be matched to a thickness of the epidermis 180.

FIG. 13 shows a sectional view of another exemplary skin resurfacingtreatment. The skin resurfacing can be non-ablative. Electromagneticradiation 200 is directed to skin 175, which includes epidermis 180,dermis 185, and a subcutaneous fat region 190. The electromagneticradiation 200 can include an array of radiation beams delivered to theskin 175 to a plurality of treatment zones 205. The electromagneticradiation 170 can cause thermal injury 205 to the epidermis 180 in thetarget region sufficient to elicit a healing response that produces asubstantially improved skin condition without detachment of theepidermis 180. The thermal injury 205 can extend into the dermis 185.The thermal injury 205 can leave the epidermis 180 intact for, e.g., upto 3 days. The optical penetration depth of the electromagneticradiation 200 can be matched to a thickness of the epidermis 180. Eachtreatment zone or thermal injury 205 can be separated by substantiallyundamaged skin 210. Healing can initiate from less injured orsubstantially undamaged skin 210 adjacent the plurality of treatmentzones.

FIG. 14 shows a sectional view of another exemplary skin resurfacingtreatment. The skin resurfacing can be non-ablative. Electromagneticradiation 215 is directed to skin 175, which includes epidermis 180,dermis 185, and a subcutaneous fat region 190. The electromagneticradiation 215 can cause thermal injury 220 to the epidermis 180 in thetarget region sufficient to elicit a healing response that produces asubstantially improved skin condition without detachment of theepidermis 180. The thermal injury 220 can extend into the dermis 185.The thermal injury 220 can leave the epidermis 180 intact for, e.g., upto 3 days. The optical penetration depth of the electromagneticradiation 215 can be matched to a thickness of the epidermis 180.

FIG. 15 shows a top view of the thermal injury 220 caused by the skinresurfacing treatment shown in FIG. 14. Treatment zone 220 surroundsregions of untreated epidermis 225 forming islands of undamaged oruntreated tissue, or undamaged or untreated tissue surrounded bysubstantially damaged or treated tissue.

FIG. 16 shows an exemplary mask 230 for forming a beam of radiation intoa patterned beam capable of forming a reverse fractional pattern, or apattern of undamaged tissue or skin surrounded by damaged tissue orskin. The mask 230 includes a substrate 233 including a coating 235. Thesubstrate 233 can be fused silica, quartz, sapphire, or infraseal. Thecoating 235 can be a dialectic and/or anti-reflective coating. Thecoating 235 can be a filter or mirrored coating. The coating 235 can bereflective, opaque or translucent. The regions between the coating 235can be uncoated or include a clear, transmitting coating.

The beam of radiation incident on the mask 230 can be collimated,convergent or divergent. The coating 235 can block the radiation at thecoated portions, and allow radiation to be transmitted through theuncoated portions of the substrate 233. In certain embodiments, thecoating is not disposed on an outer surface of the substrate 233, and isinstead disposed inside the substrate. The coating 235 can be integrallyformed on or inside the substrate 233, and can be formed inside thesubstrate by imaging the coated masked portions in the substrate orsandwiching the coating between two substrates.

Although the coating 235 is shown as squares, circular or any polygonalshape (e.g., triangular, rectangular, pentagonal, hexagonal, oroctagonal) can be used. Likewise, the substrate 233 can be circular orany polygonal shape (e.g., triangular, rectangular, pentagonal,hexagonal, or octagonal). The shape of the substrate 233 and the coating235 need not match.

The substrate 233 can be about 15 mm×15 mm. The coating 235 can be about0.5 mm to about 2 mm thick. In certain embodiments, the coating 235 isabout 1 mm.

The coated regions 235 can be 0.5 mm to about 5 mm in cross-section ordiameter. For example, the coated regions 235 can be 0.75, 1, 1.5, or 2mm in cross-section or diameter. In detailed embodiment, the coatedregions 235 is about 1 mm.

The distance between the coated regions 235 can be 100 micrometers toabout 2 mm. The distance between the coated regions 235 can be about200, 250, 500, 600, 700, 750, 1000, 1,250, or 1,500 micrometers. In onedetailed embodiment, the distance between the coated regions 235 isabout 500 micrometers. In one detailed embodiment, the distance betweenthe coated regions 235 is about 700 micrometers.

The substrate 233 can be placed directly on the skin, adjacent to theskin, or spaced from the skin. The substrate 233 can be cooled orinclude a cooling element between it and the skin.

FIG. 17 shows a sectional view of a mask 230 mounted on a coolingsubstrate 240. A space 245 between the mask 230 and the coolingsubstrate 240 can pass a cooling fluid (e.g., a cryogenic liquid,fluorinert, a cooling gas, a cooling liquid, or water) across coolingsubstrate 240.

FIG. 18 shows an exemplary pattern 250 of damage including untreatedzones 225 surrounded by a treatment region 220. The untreated zones 225correspond to a respective coated region 235. The treatment region 220can form lines of damage in the skin. The pattern 250 can promotecontraction of the skin in the treatment region 220 (e.g., bycoagulation), which results in pulling or stretching of the skin in theuntreated zones 225. As a result, the region of skin being treated canbe resurfaced, tightened, or made less lax. Collagen remodeling can alsooccur in the treatment region 220.

While the invention has been particularly shown and described withreference to specific illustrative embodiments, it should be understoodthat various changes in form and detail may be made without departingfrom the spirit and scope of the invention.

1-4. (canceled)
 5. A method of non-ablative skin resurfacing,comprising: generating electromagnetic radiation having a wavelength ofabout 1890 nm to about 1970 nm; delivering the electromagnetic radiationto a target region of skin as an array of radiation beams with anaverage fluence of about 3 J/cm² to about 6 J/cm²; and causing at leasttwo zones of thermal injury to the epidermis in the target regionsufficient to elicit a healing response that produces a substantiallyimproved skin condition without detachment of the epidermis, whereineach of the at least two zones of thermal injury is adjacent to at leastone zone of substantially undamaged epidermal tissue.
 6. The method ofclaim 5, further comprising causing at least one zone of thermal injurywhile leaving the epidermis intact for up to 3 days.
 7. The method ofclaim 5, further comprising causing at least one zone of thermal injurywhile leaving the epidermis intact for up to 7 days.
 8. The method ofclaim 5, further comprising causing at least one zone of thermal injuryto an upper portion of the dermis.
 9. The method of claim 5, furthercomprising causing cell necrosis to a depth of up to 300 micrometers inthe dermis while leaving the epidermis intact for at least 3 days. 10.The method of claim 5, further comprising causing at least one zone ofthermal injury without acute cosmetic disturbance to the epidermis. 11.The method of claim 5, further comprising matching optical penetrationdepth of the electromagnetic radiation to a thickness of the epidermis.12. The method of claim 5, further comprising exposing the target regionof skin to the electromagnetic radiation for up to 1 second.
 13. Themethod of claim 5, wherein the wavelength of the electromagneticradiation is about 1930 nm.
 14. The method of claim 5, wherein thewavelength of the electromagnetic radiation is about 1947 nm.
 15. Themethod of claim 5, wherein the wavelength of the electromagneticradiation is about 1920 nm to about 1950 nm.
 16. The method of claim 5,further comprising generating the electromagnetic radiation using apulsed source.
 17. The method of claim 5, further comprising: generatingthe electromagnetic radiation using a continuous wave source, anddelivering the electromagnetic radiation to the target region of skin asthe array of radiation beams by at least one of scanning or gating ofthe continuous wave source.
 18. The method of claim 5, furthercomprising forming a pattern in the target region of skin including aplurality of zones of thermal injury, each zone of thermal injury beingseparated from adjacent zones of thermal injury by at least one zone ofsubstantially undamaged epidermal tissue.
 19. The method of claim 5,further comprising forming a reverse fractional pattern in the targetregion of skin including a plurality of zones of substantially undamagedepidermal tissue surrounded by at least one zone of thermal injury. 20.The method of claim 5, further comprising using a thulium-doped laser togenerate the electromagnetic radiation.
 21. The method of claim 5,further comprising using a thulium:YAP laser to generate theelectromagnetic radiation.
 22. A method of non-ablative skinresurfacing, comprising: generating electromagnetic radiation having awavelength of about 1890 nm to about 1970 nm; delivering theelectromagnetic radiation to a target region of skin as an array ofradiation beams with a fluence of about 1 J/cm² to about 10 J/cm² perbeam; and causing at least one zone of thermal injury to the epidermisin the target region sufficient to elicit a healing response thatproduces a substantially improved skin condition without detachment ofthe epidermis, wherein the at least one zone of thermal injury isadjacent to at least one zone of substantially undamaged epidermaltissue.
 23. The method of claim 22, wherein the wavelength of theelectromagnetic radiation is about 1930 nm.
 24. The method of claim 22,wherein the wavelength of the electromagnetic radiation is about 1920 nmto about 1950 nm.
 25. The method of claim 22, wherein the fluence isabout 3 J/cm² to about 6 J/cm² per beam.
 26. The method of claim 22,wherein the fluence is about 5 J/cm² per beam.
 27. An apparatuscomprising: a source for generating electromagnetic radiation having awavelength of about 1890 nm to about 1970 nm; a delivery module forreceiving the electromagnetic radiation, absorbing a portion of theelectromagnetic radiation to form at least one region of untreated zone,and transmitting the remaining portion of the electromagnetic radiationto form at least one region of thermal injury adjacent to the at leastone region of untreated zone, wherein the delivery module delivers anaverage fluence of about 3 J/cm² to about 6 J/cm² to the at least oneregion of thermal injury.
 28. The apparatus of claim 27, furthercomprising a mask for absorbing the electromagnetic radiation.
 29. Theapparatus of claim 27, wherein the source is a laser diode.
 30. Theapparatus of claim 27, wherein the source is a thulium doped laser. 31.The apparatus of claim 27, wherein the at least one region of thermalinjury elicits a healing response that produces a substantially improvedskin condition without detachment of the epidermis.
 32. An apparatuscomprising: a source for generating electromagnetic radiation having awavelength of about 1890 nm to about 1970 nm and an average fluence ofabout 3 J/cm² to about 6 J/cm²; a lens array for forming theelectromagnetic radiation as an array of radiation beams; and a deliverymodule for delivering the array of radiation beams to a target area ofskin and causing at least two regions of thermal injury in the targetarea, each region of thermal injury being adjacent to at least oneregion of untreated zone.
 33. The apparatus of claim 32, wherein thesource is a laser diode.
 34. The apparatus of claim 32, wherein thesource is a thulium doped laser.
 35. The apparatus of claim 32, whereinthe at least two regions of thermal injury elicit a healing responsethat produces a substantially improved skin condition without detachmentof the epidermis.
 36. The apparatus of claim 32, wherein the wavelengthof the electromagnetic radiation is about 1930 nm.
 37. The apparatus ofclaim 32, further comprising a controller for moving the delivery modulein at least one translational direction before causing the deliverymodule to deliver the array of radiation beams.
 38. The apparatus ofclaim 32, wherein the lens array is integrated in the delivery module.